Silicon Microrefrigerator

We fabricated a silicon microrefrigerator on a 500-mum-thick substrate with the standard integrated circuit (IC) fabrication process. The cooler achieves a maximum cooling of 1degC below ambient at room temperature. Simulations show that the cooling power density for a 40times40 mum² device exceeds 500W/cm². The unique three-dimensional (3-D) geometry, current and heat spreading, different from conventional one-dimensional (1-D) thermoelectric device, contribute to this large cooling power density. A 3-D finite element electrothermal model is used to analyze non-ideal factors inside the device and predict its limits. The simulation results show that in the ideal situation, with low contact resistance, bulk silicon with 3-D geometry could cool ~20degC with a cooling power density of 1000W/cm ² despite the low thermoelectric figure-of-merit (ZT) of the material. The large cooling power density is due to the geometry dependent heat and current spreading in the device. The non-uniformity of current and Joule heating inside the substrate also contributes to the maximum cooling of silicon microrefrigerator, exceeding 30% limit given in one-dimensional thermoelectric theory DeltaT_max=0.5ZT_c ², where T_c is the cold side temperature. These devices can be used to remove hot spots on a chip